1. Field of the Invention
The present invention relates to an optical waveguide connecting structure, an optical element mounting structure and an optical fiber mounting structure. More particularly, the present invention relates to an optical waveguide connecting structure, an optical element mounting structure, and an optical fiber mounting structure, in which core layers are connected to each other to make an optical coupling by using a plurality of optical waveguide films each having the core layer covered with a clad layer on the periphery thereof, the core layer functioning as an optical waveguide.
The present application claims priority of Japanese Patent Application No.2000-232479 filed on Jul. 31, 2000, which is hereby incorporated by reference.
2. Description of the Related Art
Optical communications technology using light as a transmission medium of information is widely used. To implement the optical communications technology, an optical module is used in which optical elements such as a light emitting element and a light receiving element are mounted on an optoelectronic substrate and the optical elements are connected to each other via an optical waveguide, thus making an optical coupling. In the optical module, optical signals need to be transmitted through the optical waveguide without being attenuated. Moreover, when assembling the optical module, it is necessary to prepare an optical waveguide connecting structure, in which the optical waveguide is formed on the optoelectronic substrate in advance and to mount the optical elements by using this optical waveguide connecting structure.
FIG. 25 is a plan view schematically showing a constitution of the optical element mounting structure, in which optical elements are mounted by using a conventional optical waveguide connecting structure. In the optical element mounting structure, as shown in FIG. 25, a plurality of optical elements 102 are mounted on a base substrate (optoelectronic substrate) 101 composed of a printed circuit board or the like, and the plurality of optical elements 102 are connected to each other via optical fibers 103 functioning as the optical waveguide. A light distributor 104 may be connected at a halfway position of the optical fibers 103 if required, and optical signals are distributed through each of optical fibers 103.
In the conventional optical element mounting structure described above, since at least one or more optical fibers 103 are required for every optical element 102, a considerable number of optical fibers 103 are needed in total. Therefore, in the optical element mounting structure which requires a large number of optical elements 102, the optical fibers 103 are arranged on the base substrate 101 complicatedly.
As described above, in the conventional optical waveguide connecting structure and the optical element mounting structure, arrangement of the optical fibers functioning as the optical waveguide for making the optical coupling between the optical elements becomes complicated, which causes a problem in that it is difficult to stably fix the optical waveguide.
Specifically, in the optical element mounting structure using the conventional optical waveguide connecting structure, as shown in FIG. 25, when many optical fibers 103 functioning as the optical waveguide are required, the optical fibers 103 are apt to be loosely fixed. Accordingly, if an external force is applied thereto by contacting with an obstacle or the like, the optical fiber 103 is vibrated, and thus the optical fiber 103 tends to be damaged easily. Therefore, reliability of the optical element mounting structure is lowered. If the optical fiber is fixed firmly to the base substrate in advance in order to correct such defects, positioning of the optical fiber and the optical element becomes complicated, and thus attachment operation of the optical element takes a lot of time and labor.
In view of the above, it is an object of the present invention to provide an optical waveguide connecting structure, an optical element mounting structure, and an optical fiber mounting structure capable of easily making connection among optical waveguides with high accuracy.
According to a first aspect of the present invention, there is provided an optical waveguide connecting structure in which core layers are connected to make an optical coupling therebetween by using a plurality of optical waveguide films each having the core layers covered with a clad layer on the periphery thereof, the core layers functioning as an optical waveguide, including:
a first optical waveguide provided with a first core layer, in which a first section slightly slants relative to an optical path direction of the first core layer is set to form a small angle of approximately 5xc2x0 or less with the optical path direction and the first core layer is exposed in the first section; and
a second optical waveguide provided with a second core layer, in which the second core layer is exposed at one end portion thereof in a section forming an angle of approximately 5xc2x0 or less with the optical path direction,
wherein the first section and the second section are opposed and connected to each other while setting both of the first core layer and the second core layer at approximately a same height from a common reference surface.
In the foregoing first aspect, a preferable mode is one wherein at least one of the first optical waveguide and the second optical waveguide is formed of an optical waveguide film
Also, a preferable mode is one wherein each of the first section of the first optical waveguide and the second section of the second optical waveguide is formed of a section vertical to a surface of the first optical waveguide.
Also, a preferable mode is one wherein each of the first section of the first optical waveguide and the second section of the second optical waveguide is formed of a slant surface relative to the vertical direction to a surface of the first optical waveguide.
Also, a preferable mode is one wherein the second optical waveguide includes a mirror surface, which is formed of a third section cut obliquely relative to a thickness direction, at an other end portion at an opposite side of the one end portion of the second core layer.
Also, a preferable mode is one wherein the first optical waveguide and the second optical waveguide are formed on a base substrate.
Also, a preferable mode is one wherein the first optical waveguide is formed on a base substrate, the second optical waveguide is formed on a reference plate, and the core layer of the second optical waveguide is aligned with the core layer of the first optical waveguide at a same height from the reference plate as the reference surface by abutting the first optical waveguide to the reference plate.
Also, a preferable mode is one wherein the first optical waveguide is cut to expose a side surface of the first core layer in a section along the optical path direction from the one end portion to the other end portion.
Also, a preferable mode is one wherein the optical waveguide connecting structure further includes:
a third optical waveguide having a third core layer formed thereon and a mirror surface formed on the third core layer by cutting the third core layer obliquely relative to a thickness direction at an other end portion, the third core layer being partially exposed at a position opposed to an exposed surface of the first core layer in a side surface of the one end portion, being extended having a specified angle relative to an exposed surface of the first core layer from the exposed portion to a halfway portion, and being extended in parallel to the exposed surface of the first core layer from the halfway portion to the other end portion,
wherein the first core layer and the third core layer are connected at approximately a same height position while maintaining a relation that a mirror surface of the third core layer and the mirror surface of the second core layer are arranged to be opposed to each other.
Also, a preferable mode is one wherein at least one of the second core layer and the third core layer is adhered to the first core layer by an adhesive having approximately a same refractive index as those of the first core layer to the third core layer.
Also, a preferable mode is one wherein the two first optical waveguides are used to be arranged on a base substrate such that the optical path directions thereof form a specified angle, the second optical waveguide is provided, which has the second sections at both end portions of the core layer thereof, the second sections being opposed to the first sections of the two first optical waveguides, and the core layer of the second optical waveguide forms a curved-shape to change the optical path direction by a specific angle.
Also, a preferable mode is one wherein, instead of the second optical waveguide, an optical waveguide is used, in which a mirror surface for totally reflecting optical signals is formed at a halfway position of the core layer functioning as the optical waveguide by which the optical signals are made incident and emitted.
According to a second aspect of the present invention, there is provided an optical element mounting structure assembled by using an optical waveguide connecting structure, including:
an optical waveguide connecting structure in which core layers are connected to make an optical coupling therebetween by using a plurality of optical waveguide films each having the core layers covered with a clad layer on the periphery thereof, the core layers functioning as an optical waveguide, including: a first optical waveguide provided with a first core layer, in which a first section slightly slants relative to an optical path direction of the first core layer is set to form a small angle of approximately 5 degrees or less with the optical path direction and the first core layer is exposed in the first section; and a second optical waveguide provided with a second core layer, in which the second core layer is exposed at one end portion thereof in a section forming an angle of approximately 5 degrees or less with the optical path direction, wherein the first section and the second section are opposed and connected to each other while setting both of s the first core layer and the second core layer at approximately a same height from a common reference surface; and wherein the second optical waveguide includes a mirror surface, which is formed of a third section cut obliquely relative to a thickness direction, at an other end portion at an opposite side of the one end portion of the second core layer; and
an optical element substrate having an optical element connected thereto,
wherein the optical element substrate is disposed such that the optical element is opposed to the mirror surface of the second core layer of the third section of the second optical waveguide. core layer of the third section of the second optical waveguide.
According to a third aspect of the present invention, there is provided an optical element mounting structure, including:
a base substrate having a first optical waveguide disposed thereon; and
an optical element substrate, on which at least a second optical waveguide is disposed via a spacer and an optical element is mounted,
wherein core layers of the first optical waveguide and the second optical waveguide are exposed in sections each forming a slight angle of approximately 5xc2x0 or less with optical paths of the core layers, and
the base substrate and the optical element substrate are combined by abutting the first optical waveguide to the surface of the spacer of the optical element substrate as a reference surface such that the sections of the core layers are opposed to each other at a same height from the base substrate.
According to a fourth aspect of the present invention, there is provided an optical element mounting structure, including:
a base substrate having a first optical waveguide disposed thereon; and
an optical element substrate, on which at least a second optical waveguide is disposed via a spacer and an optical element is mounted,
wherein core layers of the first optical waveguide and second optical waveguide are exposed in sections each forming a slight angle of approximately 5xc2x0 or less with optical paths of the core layers, and
the base substrate and the optical element substrate are combined by abutting the second optical waveguide to a surface of the base substrate as a reference surface such that the sections of the core layers are opposed to each other at a same height from the base substrate.
According to a fifth aspect of the present invention, there is provided an optical element mounting structure, including:
a first optical waveguide film, in which a section of a core layer is exposed at one end portion thereof and an other end portion of the core layer exposed in a first section forming a slight angle of about 5xc2x0 or less with optical paths of the core layers at the other end portion of the first optical waveguide film;
an optical element of which any one of a light-emitting window and a light-receiving window of the optical element is connected to the section of the core layer of the first optical waveguide to form a combined body with the first optical waveguide film; and
a second optical waveguide film, in which a core layer at least at one end portion thereof is exposed in a second section forming a slight angle of 5xc2x0 or less with the optical path,
wherein both the first optical waveguide film and the second optical waveguide film are placed on a base substrate and the core layer exposed in the first section and the core layer exposed in the second section are aligned at a same height by using the base substrate as a reference surface and are adhered to each other.
According to a sixth aspect of the present invention, there is provided an optical element mounting structure, including:
a first optical waveguide film, in which a section slants relative to a film surface is formed at one end portion, a core layer of a first optical waveguide is exposed in the section, and at an other end portion of the first optical waveguide film, the other end portion of the core layer is exposed in a first section forming a slight angle of approximately 5xc2x0 or less with optical paths of the core layers;
an optical element connected to a surface of the first optical waveguide film at a position to which optical signals of the first optical waveguide totally reflected at the section are reached,
a second optical waveguide film, in which at least one end portion of a core layer is exposed in a second section forming a slight angle of approximately 5xc2x0 or less with the optical path,
wherein both the first optical waveguide film and the second optical waveguide film are placed on a base substrate and the core layer exposed in the first section and the core layer exposed in the second section are aligned at a same height from the base substrate and are adhered to each other.
According to a seventh aspect of the present invention, there is provided an optical element mounting structure, including:
a printed circuit board, in which a first optical waveguide having a core layer connected to an optical element at one end portion thereof is disposed on a base substrate, and an other end portion of the core layer of the first optical waveguide is exposed in a first section forming an angle of approximately 5xc2x0 or less with an optical path direction of the core layer; and
a second optical waveguide film on the base substrate, having a core layer exposed in a second section forming a slight angle of approximately 5xc2x0 or less with the optical path in one end portion thereof,
wherein one end of the second optical waveguide film is placed on the base substrate of the printed circuit board while setting a height of the core layer from the base substrate approximately equal to that of the core layer of the first optical waveguide, and
the core layer exposed in the second section of the second optical waveguide film and the core layer exposed in the first section of the printed circuit board are in contact with each other.
In the foregoing seventh aspect, a preferable mode is one wherein a reference plate covering a joint portion of the second optical waveguide film and the first optical waveguide is adhered onto the second optical waveguide film, and the height of the core layer of the second optical waveguide film is set equal to that of the core layer of the first optical waveguide by abutting the first optical waveguide to a surface of the reference plate.
Also, a preferable mode is one wherein the second optical waveguide film has a portion in which a width of the optical waveguide inside the second optical waveguide film is widened in a shape of a taper and a portion in which a space portion so as to cross the optical path of the core layer at the portion widened in the shape of the taper is formed, the portion being for connecting the widened core layers with interposing the space portion therebetween, and
the space portion is formed to have a curved shape in which a width of the space in the direction of the optical path is widened as getting away from an optical axis of the core layer in a vertical direction.
According to an eighth aspect of the present invention, there is provided an optical fiber mounting structure, including:
a first optical waveguide film, in which, a fourth section slightly slants at approximately 5xc2x0 or less relative to a film surface thereof is formed at one end portion, one end portion of a core layer is exposed in the fourth section, a first section is formed at an other portion of the core layer, the first section being approximately vertical to the film surface of the first optical waveguide film and forming an angle of approximately 5xc2x0 or less with an optical path direction of the core layer;
an optical fiber having a section cut at an angle of approximately 5xc2x0 or less respective to a core layer direction, the optical fiber being connected to the fourth section of the first optical waveguide film by aligning the core layers thereof; and
a second optical waveguide film in which at least one end portion of the core layer is exposed in a second section vertical to the film surface and slightly slants at approximately 5xc2x0 or less relative to the optical path,
wherein both of the first optical waveguide film and the second optical waveguide film are placed on a base substrate and a height from the base substrate of the core layer exposed in the first section and that of the core layer exposed in the second section are set equal and adhered to each other.
With the above configurations, according to the optical waveguide mounting structure, optical element mounting structure, and the optical fiber mounting structure of the present invention, the first optical waveguide film, which is cut such that the first core layer is exposed in the slightly slant section forming an angle of 5xc2x0 or less with the optical path direction, and the second optical waveguide film, in which the exposure surface of the second core layer is formed in the slightly slant section forming an angle of about 5xc2x0 or less with the optical path of the core layer at the position opposed to the exposed surface of the first core layer in the side surface of the one end portion, are provided. The first core layer and second core layer are connected at approximately the same height position from the reference surface. Thus, the optical waveguide for performing the optical transmission can be stably fixed. Therefore, optical coupling between the optical waveguides can be easily performed with high accuracy.